The Greendale study group reunites. Jeff butts heads with the new biology teacher and Dean Pelton finds a new nemesis in the dean of the Air Conditioning Repair Annex.
Chang gets used to his new job. Britta reacts to a friend being taken hostage in a foreign country. Annie asks the group to help bring down her new friend. Professor Cligoris struggles to behave appropriately.
When the gang accepts a new person into the group, they learn how delicate their friendships really are.
New roommates Troy and Abed host an apartment-warming party that takes a strange turn.
The gang tells scary stories while Britta discovers that one of her pals might be a psychopathic maniac.
Pierce is excited about a party he's throwing to celebrate his business success, but the affair becomes very different when his elderly father arrives.
The study group pitches in to help when Annie decides to move in with Troy and Abed, but the plan breaks down when she becomes frustrated by their fun-loving lifestyle. Elsewhere, Dean Pelton discovers Jeff at the mall and blackmails him into spending a lovely afternoon together.
When the school board asks Dean Pelton to make a new commercial for the school, he enlists the study group to star in his production. Meanwhile, Abed films all the activities for a documentary.
Jeff and Shirley bond over foosball. After Annie breaks Abed's special edition DVD of "The Dark Knight", she covers it up by staging a robbery.
When the Greendale Glee Club is unexpectedly sidelined, the school's effervescent choir director Cory Radison sets about recruiting the study group members to fill in. Skeptical at first, they eventually fall under his hypnotic spell, singing and dancing their way to the annual Christmas Pageant.
Andre proposes that he and Shirley remarry and a wedding date is set. Britta and Annie get busy planning the wedding and Jeff prepares to give a wedding speech, while Troy and Abed get ready to be "normal" for the occasion. Meanwhile, Pierce and Shirley pitch a sandwich shop idea to Dean Pelton for the Greendale cafeteria.
Jeff begins experiencing extreme narcissism. The group helps Abed get rid of debt by impersonating various celebrities at a Bar Mitzvah.
As the new Greendale Subway shop opens in the cafeteria, Shirley, Pierce and Britta plot to bring about its early demise. Vice Dean Laybourne makes another attempt to get Troy to join the Air Conditioning Repair Annex, while Abed and Troy find themselves at odds over their competing pillow and blanket forts.
The war between Abed and Troy intensifies, prompting Jeff to try to negotiate a truce between the former best friends while the rest of the group choose sides.
Annie, Troy and Abed try to help Britta avoid an old flame who has returned to town, while Jeff and Shirley set out to catch a glimpse of the mystery man. Elsewhere, Laybourne turns to Dean Pelton for help with his pursuit of Troy.
When a final exam is postponed, Annie talks Abed into letting her spend some time in the dreamatorium, where an innocent simulation turns into an examination of the study group.
In a homage to Law & Order, the study group investigate a crime when someone sabotages their science experiment. When they discover the perp, Annie plans on prosecuting them to the fullest extent of Greendale's Code of Conduct.
When a beloved classmate dies unexpectedly, Britta uses skills from psychology class to counsel the study group. Chang tries to seize more control over campus security.
Abed becomes convinced that there is a conspiracy afoot and that Dean Pelton is an imposter. When Abed is apprehended sneaking around on campus, he is required to see a therapist, or risk being sent to jail.
Pierce is summoned to Hawthorne Enterprises to discuss his inheritance with his deceased father's former right-hand man, Gilbert Lawson. The study group goes with him for moral support and must all pitch in to play the video game of their life on Pierce's behalf for the sake of his inheritance.
When Chang gains control of Greendale's campus, the study group forms a plot to take back the school. Troy seeks help at the Air Conditioning Repair Annex.
Jeff and and his former colleague Alan battle in court as opposing counsel in Pierce and Shirley's sandwich shop case. Meanwhile, Vice Dean Laybourne makes one last ditch effort to win Troy over to his Air Conditioning Repair Annex.